// Copyright (c) 2021, gottingen group.
// All rights reserved.
// Created by liyinbin lijippy@163.com

#include "abel/container/internal/layout.h"
// We need ::max_align_t because some libstdc++ versions don't provide
// std::max_align_t
#include <stddef.h>
#include <cstdint>
#include <memory>
#include <sstream>
#include <type_traits>

#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "abel/log/logging.h"
#include "abel/utility/span.h"

namespace abel {

    namespace container_internal {
        namespace {

            using ::abel::span;
            using ::testing::ElementsAre;

            size_t Distance(const void *from, const void *to) {
                DCHECK(from <= to, "Distance must be non-negative");
                return static_cast<const char *>(to) - static_cast<const char *>(from);
            }

            template<class Expected, class Actual>
            Expected Type(Actual val) {
                static_assert(std::is_same<Expected, Actual>(), "");
                return val;
            }

// Helper classes to test different size and alignments.
            struct alignas(8) Int128 {
                uint64_t a, b;

                friend bool operator==(Int128 lhs, Int128 rhs) {
                    return std::tie(lhs.a, lhs.b) == std::tie(rhs.a, rhs.b);
                }

                static std::string Name() {
                    return internal_layout::adl_barrier::TypeName<Int128>();
                }
            };

// int64_t is *not* 8-byte aligned on all platforms!
            struct alignas(8) Int64 {
                int64_t a;

                friend bool operator==(Int64 lhs, Int64 rhs) {
                    return lhs.a == rhs.a;
                }
            };

// Properties of types that this test relies on.
            static_assert(sizeof(int8_t) == 1, "");
            static_assert(alignof(int8_t) == 1, "");
            static_assert(sizeof(int16_t) == 2, "");
            static_assert(alignof(int16_t) == 2, "");
            static_assert(sizeof(int32_t) == 4, "");
            static_assert(alignof(int32_t) == 4, "");
            static_assert(sizeof(Int64) == 8, "");
            static_assert(alignof(Int64) == 8, "");
            static_assert(sizeof(Int128) == 16, "");
            static_assert(alignof(Int128) == 8, "");

            template<class Expected, class Actual>
            void SameType() {
                static_assert(std::is_same<Expected, Actual>(), "");
            }

            TEST(Layout, element_type) {
                {
                    using L = Layout<int32_t>;
                    SameType<int32_t, L::element_type < 0>>
                    ();
                    SameType<int32_t, decltype(L::Partial())::element_type<0>>();
                    SameType<int32_t, decltype(L::Partial(0))::element_type<0>>();
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    SameType<int32_t, L::element_type < 0>>
                    ();
                    SameType<int32_t, L::element_type < 1>>
                    ();
                    SameType<int32_t, decltype(L::Partial())::element_type<0>>();
                    SameType<int32_t, decltype(L::Partial())::element_type<1>>();
                    SameType<int32_t, decltype(L::Partial(0))::element_type<0>>();
                    SameType<int32_t, decltype(L::Partial(0))::element_type<1>>();
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    SameType<int8_t, L::element_type < 0>>
                    ();
                    SameType<int32_t, L::element_type < 1>>
                    ();
                    SameType<Int128, L::element_type < 2>>
                    ();
                    SameType<int8_t, decltype(L::Partial())::element_type<0>>();
                    SameType<int8_t, decltype(L::Partial(0))::element_type<0>>();
                    SameType<int32_t, decltype(L::Partial(0))::element_type<1>>();
                    SameType<int8_t, decltype(L::Partial(0, 0))::element_type<0>>();
                    SameType<int32_t, decltype(L::Partial(0, 0))::element_type<1>>();
                    SameType<Int128, decltype(L::Partial(0, 0))::element_type<2>>();
                    SameType<int8_t, decltype(L::Partial(0, 0, 0))::element_type<0>>();
                    SameType<int32_t, decltype(L::Partial(0, 0, 0))::element_type<1>>();
                    SameType<Int128, decltype(L::Partial(0, 0, 0))::element_type<2>>();
                }
            }

            TEST(Layout, ElementTypes) {
                {
                    using L = Layout<int32_t>;
                    SameType<std::tuple<int32_t>, L::ElementTypes>();
                    SameType<std::tuple<int32_t>, decltype(L::Partial())::ElementTypes>();
                    SameType<std::tuple<int32_t>, decltype(L::Partial(0))::ElementTypes>();
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    SameType<std::tuple<int32_t, int32_t>, L::ElementTypes>();
                    SameType<std::tuple<int32_t, int32_t>, decltype(L::Partial())::ElementTypes>();
                    SameType<std::tuple<int32_t, int32_t>, decltype(L::Partial(0))::ElementTypes>();
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    SameType<std::tuple<int8_t, int32_t, Int128>, L::ElementTypes>();
                    SameType<std::tuple<int8_t, int32_t, Int128>,
                            decltype(L::Partial())::ElementTypes>();
                    SameType<std::tuple<int8_t, int32_t, Int128>,
                            decltype(L::Partial(0))::ElementTypes>();
                    SameType<std::tuple<int8_t, int32_t, Int128>,
                            decltype(L::Partial(0, 0))::ElementTypes>();
                    SameType<std::tuple<int8_t, int32_t, Int128>,
                            decltype(L::Partial(0, 0, 0))::ElementTypes>();
                }
            }

            TEST(Layout, OffsetByIndex) {
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, L::Partial().Offset<0>());
                    EXPECT_EQ(0, L::Partial(3).Offset<0>());
                    EXPECT_EQ(0, L(3).Offset<0>());
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_EQ(0, L::Partial().Offset<0>());
                    EXPECT_EQ(0, L::Partial(3).Offset<0>());
                    EXPECT_EQ(12, L::Partial(3).Offset<1>());
                    EXPECT_EQ(0, L::Partial(3, 5).Offset<0>());
                    EXPECT_EQ(12, L::Partial(3, 5).Offset<1>());
                    EXPECT_EQ(0, L(3, 5).Offset<0>());
                    EXPECT_EQ(12, L(3, 5).Offset<1>());
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(0, L::Partial().Offset<0>());
                    EXPECT_EQ(0, L::Partial(0).Offset<0>());
                    EXPECT_EQ(0, L::Partial(0).Offset<1>());
                    EXPECT_EQ(0, L::Partial(1).Offset<0>());
                    EXPECT_EQ(4, L::Partial(1).Offset<1>());
                    EXPECT_EQ(0, L::Partial(5).Offset<0>());
                    EXPECT_EQ(8, L::Partial(5).Offset<1>());
                    EXPECT_EQ(0, L::Partial(0, 0).Offset<0>());
                    EXPECT_EQ(0, L::Partial(0, 0).Offset<1>());
                    EXPECT_EQ(0, L::Partial(0, 0).Offset<2>());
                    EXPECT_EQ(0, L::Partial(1, 0).Offset<0>());
                    EXPECT_EQ(4, L::Partial(1, 0).Offset<1>());
                    EXPECT_EQ(8, L::Partial(1, 0).Offset<2>());
                    EXPECT_EQ(0, L::Partial(5, 3).Offset<0>());
                    EXPECT_EQ(8, L::Partial(5, 3).Offset<1>());
                    EXPECT_EQ(24, L::Partial(5, 3).Offset<2>());
                    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<0>());
                    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<1>());
                    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<2>());
                    EXPECT_EQ(0, L::Partial(1, 0, 0).Offset<0>());
                    EXPECT_EQ(4, L::Partial(1, 0, 0).Offset<1>());
                    EXPECT_EQ(8, L::Partial(1, 0, 0).Offset<2>());
                    EXPECT_EQ(0, L::Partial(5, 3, 1).Offset<0>());
                    EXPECT_EQ(24, L::Partial(5, 3, 1).Offset<2>());
                    EXPECT_EQ(8, L::Partial(5, 3, 1).Offset<1>());
                    EXPECT_EQ(0, L(5, 3, 1).Offset<0>());
                    EXPECT_EQ(24, L(5, 3, 1).Offset<2>());
                    EXPECT_EQ(8, L(5, 3, 1).Offset<1>());
                }
            }

            TEST(Layout, OffsetByType) {
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, L::Partial().Offset<int32_t>());
                    EXPECT_EQ(0, L::Partial(3).Offset<int32_t>());
                    EXPECT_EQ(0, L(3).Offset<int32_t>());
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(0, L::Partial().Offset<int8_t>());
                    EXPECT_EQ(0, L::Partial(0).Offset<int8_t>());
                    EXPECT_EQ(0, L::Partial(0).Offset<int32_t>());
                    EXPECT_EQ(0, L::Partial(1).Offset<int8_t>());
                    EXPECT_EQ(4, L::Partial(1).Offset<int32_t>());
                    EXPECT_EQ(0, L::Partial(5).Offset<int8_t>());
                    EXPECT_EQ(8, L::Partial(5).Offset<int32_t>());
                    EXPECT_EQ(0, L::Partial(0, 0).Offset<int8_t>());
                    EXPECT_EQ(0, L::Partial(0, 0).Offset<int32_t>());
                    EXPECT_EQ(0, L::Partial(0, 0).Offset<Int128>());
                    EXPECT_EQ(0, L::Partial(1, 0).Offset<int8_t>());
                    EXPECT_EQ(4, L::Partial(1, 0).Offset<int32_t>());
                    EXPECT_EQ(8, L::Partial(1, 0).Offset<Int128>());
                    EXPECT_EQ(0, L::Partial(5, 3).Offset<int8_t>());
                    EXPECT_EQ(8, L::Partial(5, 3).Offset<int32_t>());
                    EXPECT_EQ(24, L::Partial(5, 3).Offset<Int128>());
                    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<int8_t>());
                    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<int32_t>());
                    EXPECT_EQ(0, L::Partial(0, 0, 0).Offset<Int128>());
                    EXPECT_EQ(0, L::Partial(1, 0, 0).Offset<int8_t>());
                    EXPECT_EQ(4, L::Partial(1, 0, 0).Offset<int32_t>());
                    EXPECT_EQ(8, L::Partial(1, 0, 0).Offset<Int128>());
                    EXPECT_EQ(0, L::Partial(5, 3, 1).Offset<int8_t>());
                    EXPECT_EQ(24, L::Partial(5, 3, 1).Offset<Int128>());
                    EXPECT_EQ(8, L::Partial(5, 3, 1).Offset<int32_t>());
                    EXPECT_EQ(0, L(5, 3, 1).Offset<int8_t>());
                    EXPECT_EQ(24, L(5, 3, 1).Offset<Int128>());
                    EXPECT_EQ(8, L(5, 3, 1).Offset<int32_t>());
                }
            }

            TEST(Layout, Offsets) {
                {
                    using L = Layout<int32_t>;
                    EXPECT_THAT(L::Partial().Offsets(), ElementsAre(0));
                    EXPECT_THAT(L::Partial(3).Offsets(), ElementsAre(0));
                    EXPECT_THAT(L(3).Offsets(), ElementsAre(0));
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_THAT(L::Partial().Offsets(), ElementsAre(0));
                    EXPECT_THAT(L::Partial(3).Offsets(), ElementsAre(0, 12));
                    EXPECT_THAT(L::Partial(3, 5).Offsets(), ElementsAre(0, 12));
                    EXPECT_THAT(L(3, 5).Offsets(), ElementsAre(0, 12));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_THAT(L::Partial().Offsets(), ElementsAre(0));
                    EXPECT_THAT(L::Partial(1).Offsets(), ElementsAre(0, 4));
                    EXPECT_THAT(L::Partial(5).Offsets(), ElementsAre(0, 8));
                    EXPECT_THAT(L::Partial(0, 0).Offsets(), ElementsAre(0, 0, 0));
                    EXPECT_THAT(L::Partial(1, 0).Offsets(), ElementsAre(0, 4, 8));
                    EXPECT_THAT(L::Partial(5, 3).Offsets(), ElementsAre(0, 8, 24));
                    EXPECT_THAT(L::Partial(0, 0, 0).Offsets(), ElementsAre(0, 0, 0));
                    EXPECT_THAT(L::Partial(1, 0, 0).Offsets(), ElementsAre(0, 4, 8));
                    EXPECT_THAT(L::Partial(5, 3, 1).Offsets(), ElementsAre(0, 8, 24));
                    EXPECT_THAT(L(5, 3, 1).Offsets(), ElementsAre(0, 8, 24));
                }
            }

            TEST(Layout, AllocSize) {
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, L::Partial(0).AllocSize());
                    EXPECT_EQ(12, L::Partial(3).AllocSize());
                    EXPECT_EQ(12, L(3).AllocSize());
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_EQ(32, L::Partial(3, 5).AllocSize());
                    EXPECT_EQ(32, L(3, 5).AllocSize());
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(0, L::Partial(0, 0, 0).AllocSize());
                    EXPECT_EQ(8, L::Partial(1, 0, 0).AllocSize());
                    EXPECT_EQ(8, L::Partial(0, 1, 0).AllocSize());
                    EXPECT_EQ(16, L::Partial(0, 0, 1).AllocSize());
                    EXPECT_EQ(24, L::Partial(1, 1, 1).AllocSize());
                    EXPECT_EQ(136, L::Partial(3, 5, 7).AllocSize());
                    EXPECT_EQ(136, L(3, 5, 7).AllocSize());
                }
            }

            TEST(Layout, SizeByIndex) {
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, L::Partial(0).Size<0>());
                    EXPECT_EQ(3, L::Partial(3).Size<0>());
                    EXPECT_EQ(3, L(3).Size<0>());
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_EQ(0, L::Partial(0).Size<0>());
                    EXPECT_EQ(3, L::Partial(3).Size<0>());
                    EXPECT_EQ(3, L::Partial(3, 5).Size<0>());
                    EXPECT_EQ(5, L::Partial(3, 5).Size<1>());
                    EXPECT_EQ(3, L(3, 5).Size<0>());
                    EXPECT_EQ(5, L(3, 5).Size<1>());
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(3, L::Partial(3).Size<0>());
                    EXPECT_EQ(3, L::Partial(3, 5).Size<0>());
                    EXPECT_EQ(5, L::Partial(3, 5).Size<1>());
                    EXPECT_EQ(3, L::Partial(3, 5, 7).Size<0>());
                    EXPECT_EQ(5, L::Partial(3, 5, 7).Size<1>());
                    EXPECT_EQ(7, L::Partial(3, 5, 7).Size<2>());
                    EXPECT_EQ(3, L(3, 5, 7).Size<0>());
                    EXPECT_EQ(5, L(3, 5, 7).Size<1>());
                    EXPECT_EQ(7, L(3, 5, 7).Size<2>());
                }
            }

            TEST(Layout, SizeByType) {
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, L::Partial(0).Size<int32_t>());
                    EXPECT_EQ(3, L::Partial(3).Size<int32_t>());
                    EXPECT_EQ(3, L(3).Size<int32_t>());
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(3, L::Partial(3).Size<int8_t>());
                    EXPECT_EQ(3, L::Partial(3, 5).Size<int8_t>());
                    EXPECT_EQ(5, L::Partial(3, 5).Size<int32_t>());
                    EXPECT_EQ(3, L::Partial(3, 5, 7).Size<int8_t>());
                    EXPECT_EQ(5, L::Partial(3, 5, 7).Size<int32_t>());
                    EXPECT_EQ(7, L::Partial(3, 5, 7).Size<Int128>());
                    EXPECT_EQ(3, L(3, 5, 7).Size<int8_t>());
                    EXPECT_EQ(5, L(3, 5, 7).Size<int32_t>());
                    EXPECT_EQ(7, L(3, 5, 7).Size<Int128>());
                }
            }

            TEST(Layout, Sizes) {
                {
                    using L = Layout<int32_t>;
                    EXPECT_THAT(L::Partial().Sizes(), ElementsAre());
                    EXPECT_THAT(L::Partial(3).Sizes(), ElementsAre(3));
                    EXPECT_THAT(L(3).Sizes(), ElementsAre(3));
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_THAT(L::Partial().Sizes(), ElementsAre());
                    EXPECT_THAT(L::Partial(3).Sizes(), ElementsAre(3));
                    EXPECT_THAT(L::Partial(3, 5).Sizes(), ElementsAre(3, 5));
                    EXPECT_THAT(L(3, 5).Sizes(), ElementsAre(3, 5));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_THAT(L::Partial().Sizes(), ElementsAre());
                    EXPECT_THAT(L::Partial(3).Sizes(), ElementsAre(3));
                    EXPECT_THAT(L::Partial(3, 5).Sizes(), ElementsAre(3, 5));
                    EXPECT_THAT(L::Partial(3, 5, 7).Sizes(), ElementsAre(3, 5, 7));
                    EXPECT_THAT(L(3, 5, 7).Sizes(), ElementsAre(3, 5, 7));
                }
            }

            TEST(Layout, PointerByIndex) {
                alignas(max_align_t) const unsigned char p[100] = {};
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, Distance(p, Type<const int32_t *>(L::Partial().Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int32_t *>(L::Partial(3).Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int32_t *>(L(3).Pointer<0>(p))));
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_EQ(0, Distance(p, Type<const int32_t *>(L::Partial().Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int32_t *>(L::Partial(3).Pointer<0>(p))));
                    EXPECT_EQ(12, Distance(p, Type<const int32_t *>(L::Partial(3).Pointer<1>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int32_t *>(L::Partial(3, 5).Pointer<0>(p))));
                    EXPECT_EQ(12,
                              Distance(p, Type<const int32_t *>(L::Partial(3, 5).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int32_t *>(L(3, 5).Pointer<0>(p))));
                    EXPECT_EQ(12, Distance(p, Type<const int32_t *>(L(3, 5).Pointer<1>(p))));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(0, Distance(p, Type<const int8_t *>(L::Partial().Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int8_t *>(L::Partial(0).Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int32_t *>(L::Partial(0).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int8_t *>(L::Partial(1).Pointer<0>(p))));
                    EXPECT_EQ(4, Distance(p, Type<const int32_t *>(L::Partial(1).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int8_t *>(L::Partial(5).Pointer<0>(p))));
                    EXPECT_EQ(8, Distance(p, Type<const int32_t *>(L::Partial(5).Pointer<1>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int8_t *>(L::Partial(0, 0).Pointer<0>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int32_t *>(L::Partial(0, 0).Pointer<1>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const Int128 *>(L::Partial(0, 0).Pointer<2>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int8_t *>(L::Partial(1, 0).Pointer<0>(p))));
                    EXPECT_EQ(4,
                              Distance(p, Type<const int32_t *>(L::Partial(1, 0).Pointer<1>(p))));
                    EXPECT_EQ(8,
                              Distance(p, Type<const Int128 *>(L::Partial(1, 0).Pointer<2>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int8_t *>(L::Partial(5, 3).Pointer<0>(p))));
                    EXPECT_EQ(8,
                              Distance(p, Type<const int32_t *>(L::Partial(5, 3).Pointer<1>(p))));
                    EXPECT_EQ(24,
                              Distance(p, Type<const Int128 *>(L::Partial(5, 3).Pointer<2>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<const int8_t *>(L::Partial(0, 0, 0).Pointer<0>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<const int32_t *>(L::Partial(0, 0, 0).Pointer<1>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<const Int128 *>(L::Partial(0, 0, 0).Pointer<2>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<const int8_t *>(L::Partial(1, 0, 0).Pointer<0>(p))));
                    EXPECT_EQ(
                            4, Distance(p, Type<const int32_t *>(L::Partial(1, 0, 0).Pointer<1>(p))));
                    EXPECT_EQ(
                            8, Distance(p, Type<const Int128 *>(L::Partial(1, 0, 0).Pointer<2>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<const int8_t *>(L::Partial(5, 3, 1).Pointer<0>(p))));
                    EXPECT_EQ(
                            24,
                            Distance(p, Type<const Int128 *>(L::Partial(5, 3, 1).Pointer<2>(p))));
                    EXPECT_EQ(
                            8, Distance(p, Type<const int32_t *>(L::Partial(5, 3, 1).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int8_t *>(L(5, 3, 1).Pointer<0>(p))));
                    EXPECT_EQ(24, Distance(p, Type<const Int128 *>(L(5, 3, 1).Pointer<2>(p))));
                    EXPECT_EQ(8, Distance(p, Type<const int32_t *>(L(5, 3, 1).Pointer<1>(p))));
                }
            }

            TEST(Layout, PointerByType) {
                alignas(max_align_t) const unsigned char p[100] = {};
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0,
                              Distance(p, Type<const int32_t *>(L::Partial().Pointer<int32_t>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int32_t *>(L::Partial(3).Pointer<int32_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const int32_t *>(L(3).Pointer<int32_t>(p))));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(0, Distance(p, Type<const int8_t *>(L::Partial().Pointer<int8_t>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int8_t *>(L::Partial(0).Pointer<int8_t>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int32_t *>(L::Partial(0).Pointer<int32_t>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int8_t *>(L::Partial(1).Pointer<int8_t>(p))));
                    EXPECT_EQ(4,
                              Distance(p, Type<const int32_t *>(L::Partial(1).Pointer<int32_t>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<const int8_t *>(L::Partial(5).Pointer<int8_t>(p))));
                    EXPECT_EQ(8,
                              Distance(p, Type<const int32_t *>(L::Partial(5).Pointer<int32_t>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<const int8_t *>(L::Partial(0, 0).Pointer<int8_t>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<const int32_t *>(L::Partial(0, 0).Pointer<int32_t>(p))));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<const Int128 *>(L::Partial(0, 0).Pointer<Int128>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<const int8_t *>(L::Partial(1, 0).Pointer<int8_t>(p))));
                    EXPECT_EQ(
                            4, Distance(p, Type<const int32_t *>(L::Partial(1, 0).Pointer<int32_t>(p))));
                    EXPECT_EQ(
                            8,
                            Distance(p, Type<const Int128 *>(L::Partial(1, 0).Pointer<Int128>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<const int8_t *>(L::Partial(5, 3).Pointer<int8_t>(p))));
                    EXPECT_EQ(
                            8, Distance(p, Type<const int32_t *>(L::Partial(5, 3).Pointer<int32_t>(p))));
                    EXPECT_EQ(
                            24,
                            Distance(p, Type<const Int128 *>(L::Partial(5, 3).Pointer<Int128>(p))));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<const int8_t *>(L::Partial(0, 0, 0).Pointer<int8_t>(p))));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<const int32_t *>(L::Partial(0, 0, 0).Pointer<int32_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<const Int128 *>(
                            L::Partial(0, 0, 0).Pointer<Int128>(p))));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<const int8_t *>(L::Partial(1, 0, 0).Pointer<int8_t>(p))));
                    EXPECT_EQ(
                            4,
                            Distance(p, Type<const int32_t *>(L::Partial(1, 0, 0).Pointer<int32_t>(p))));
                    EXPECT_EQ(8, Distance(p, Type<const Int128 *>(
                            L::Partial(1, 0, 0).Pointer<Int128>(p))));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<const int8_t *>(L::Partial(5, 3, 1).Pointer<int8_t>(p))));
                    EXPECT_EQ(24, Distance(p, Type<const Int128 *>(
                            L::Partial(5, 3, 1).Pointer<Int128>(p))));
                    EXPECT_EQ(
                            8,
                            Distance(p, Type<const int32_t *>(L::Partial(5, 3, 1).Pointer<int32_t>(p))));
                    EXPECT_EQ(24,
                              Distance(p, Type<const Int128 *>(L(5, 3, 1).Pointer<Int128>(p))));
                    EXPECT_EQ(8, Distance(p, Type<const int32_t *>(L(5, 3, 1).Pointer<int32_t>(p))));
                }
            }

            TEST(Layout, MutablePointerByIndex) {
                alignas(max_align_t) unsigned char p[100];
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial().Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial(3).Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L(3).Pointer<0>(p))));
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial().Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial(3).Pointer<0>(p))));
                    EXPECT_EQ(12, Distance(p, Type<int32_t *>(L::Partial(3).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial(3, 5).Pointer<0>(p))));
                    EXPECT_EQ(12, Distance(p, Type<int32_t *>(L::Partial(3, 5).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L(3, 5).Pointer<0>(p))));
                    EXPECT_EQ(12, Distance(p, Type<int32_t *>(L(3, 5).Pointer<1>(p))));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial().Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(0).Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial(0).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(1).Pointer<0>(p))));
                    EXPECT_EQ(4, Distance(p, Type<int32_t *>(L::Partial(1).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(5).Pointer<0>(p))));
                    EXPECT_EQ(8, Distance(p, Type<int32_t *>(L::Partial(5).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(0, 0).Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial(0, 0).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<Int128 *>(L::Partial(0, 0).Pointer<2>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(1, 0).Pointer<0>(p))));
                    EXPECT_EQ(4, Distance(p, Type<int32_t *>(L::Partial(1, 0).Pointer<1>(p))));
                    EXPECT_EQ(8, Distance(p, Type<Int128 *>(L::Partial(1, 0).Pointer<2>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(5, 3).Pointer<0>(p))));
                    EXPECT_EQ(8, Distance(p, Type<int32_t *>(L::Partial(5, 3).Pointer<1>(p))));
                    EXPECT_EQ(24, Distance(p, Type<Int128 *>(L::Partial(5, 3).Pointer<2>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(0, 0, 0).Pointer<0>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial(0, 0, 0).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<Int128 *>(L::Partial(0, 0, 0).Pointer<2>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(1, 0, 0).Pointer<0>(p))));
                    EXPECT_EQ(4, Distance(p, Type<int32_t *>(L::Partial(1, 0, 0).Pointer<1>(p))));
                    EXPECT_EQ(8, Distance(p, Type<Int128 *>(L::Partial(1, 0, 0).Pointer<2>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(5, 3, 1).Pointer<0>(p))));
                    EXPECT_EQ(24,
                              Distance(p, Type<Int128 *>(L::Partial(5, 3, 1).Pointer<2>(p))));
                    EXPECT_EQ(8, Distance(p, Type<int32_t *>(L::Partial(5, 3, 1).Pointer<1>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L(5, 3, 1).Pointer<0>(p))));
                    EXPECT_EQ(24, Distance(p, Type<Int128 *>(L(5, 3, 1).Pointer<2>(p))));
                    EXPECT_EQ(8, Distance(p, Type<int32_t *>(L(5, 3, 1).Pointer<1>(p))));
                }
            }

            TEST(Layout, MutablePointerByType) {
                alignas(max_align_t) unsigned char p[100];
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial().Pointer<int32_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial(3).Pointer<int32_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L(3).Pointer<int32_t>(p))));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial().Pointer<int8_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(0).Pointer<int8_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial(0).Pointer<int32_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(1).Pointer<int8_t>(p))));
                    EXPECT_EQ(4, Distance(p, Type<int32_t *>(L::Partial(1).Pointer<int32_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(5).Pointer<int8_t>(p))));
                    EXPECT_EQ(8, Distance(p, Type<int32_t *>(L::Partial(5).Pointer<int32_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(0, 0).Pointer<int8_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int32_t *>(L::Partial(0, 0).Pointer<int32_t>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<Int128 *>(L::Partial(0, 0).Pointer<Int128>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(1, 0).Pointer<int8_t>(p))));
                    EXPECT_EQ(4, Distance(p, Type<int32_t *>(L::Partial(1, 0).Pointer<int32_t>(p))));
                    EXPECT_EQ(8,
                              Distance(p, Type<Int128 *>(L::Partial(1, 0).Pointer<Int128>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L::Partial(5, 3).Pointer<int8_t>(p))));
                    EXPECT_EQ(8, Distance(p, Type<int32_t *>(L::Partial(5, 3).Pointer<int32_t>(p))));
                    EXPECT_EQ(24,
                              Distance(p, Type<Int128 *>(L::Partial(5, 3).Pointer<Int128>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<int8_t *>(L::Partial(0, 0, 0).Pointer<int8_t>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<int32_t *>(L::Partial(0, 0, 0).Pointer<int32_t>(p))));
                    EXPECT_EQ(
                            0, Distance(p, Type<Int128 *>(L::Partial(0, 0, 0).Pointer<Int128>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<int8_t *>(L::Partial(1, 0, 0).Pointer<int8_t>(p))));
                    EXPECT_EQ(4,
                              Distance(p, Type<int32_t *>(L::Partial(1, 0, 0).Pointer<int32_t>(p))));
                    EXPECT_EQ(
                            8, Distance(p, Type<Int128 *>(L::Partial(1, 0, 0).Pointer<Int128>(p))));
                    EXPECT_EQ(0,
                              Distance(p, Type<int8_t *>(L::Partial(5, 3, 1).Pointer<int8_t>(p))));
                    EXPECT_EQ(
                            24, Distance(p, Type<Int128 *>(L::Partial(5, 3, 1).Pointer<Int128>(p))));
                    EXPECT_EQ(8,
                              Distance(p, Type<int32_t *>(L::Partial(5, 3, 1).Pointer<int32_t>(p))));
                    EXPECT_EQ(0, Distance(p, Type<int8_t *>(L(5, 3, 1).Pointer<int8_t>(p))));
                    EXPECT_EQ(24, Distance(p, Type<Int128 *>(L(5, 3, 1).Pointer<Int128>(p))));
                    EXPECT_EQ(8, Distance(p, Type<int32_t *>(L(5, 3, 1).Pointer<int32_t>(p))));
                }
            }

            TEST(Layout, Pointers) {
                alignas(max_align_t) const unsigned char p[100] = {};
                using L = Layout<int8_t, int8_t, Int128>;
                {
                    const auto x = L::Partial();
                    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p)),
                              Type<std::tuple<const int8_t *>>(x.Pointers(p)));
                }
                {
                    const auto x = L::Partial(1);
                    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p)),
                              (Type<std::tuple<const int8_t *, const int8_t *>>(x.Pointers(p))));
                }
                {
                    const auto x = L::Partial(1, 2);
                    EXPECT_EQ(
                            std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
                            (Type<std::tuple<const int8_t *, const int8_t *, const Int128 *>>(
                                    x.Pointers(p))));
                }
                {
                    const auto x = L::Partial(1, 2, 3);
                    EXPECT_EQ(
                            std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
                            (Type<std::tuple<const int8_t *, const int8_t *, const Int128 *>>(
                                    x.Pointers(p))));
                }
                {
                    const L x(1, 2, 3);
                    EXPECT_EQ(
                            std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
                            (Type<std::tuple<const int8_t *, const int8_t *, const Int128 *>>(
                                    x.Pointers(p))));
                }
            }

            TEST(Layout, MutablePointers) {
                alignas(max_align_t) unsigned char p[100];
                using L = Layout<int8_t, int8_t, Int128>;
                {
                    const auto x = L::Partial();
                    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p)),
                              Type<std::tuple<int8_t *>>(x.Pointers(p)));
                }
                {
                    const auto x = L::Partial(1);
                    EXPECT_EQ(std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p)),
                              (Type<std::tuple<int8_t *, int8_t *>>(x.Pointers(p))));
                }
                {
                    const auto x = L::Partial(1, 2);
                    EXPECT_EQ(
                            std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
                            (Type<std::tuple<int8_t *, int8_t *, Int128 *>>(x.Pointers(p))));
                }
                {
                    const auto x = L::Partial(1, 2, 3);
                    EXPECT_EQ(
                            std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
                            (Type<std::tuple<int8_t *, int8_t *, Int128 *>>(x.Pointers(p))));
                }
                {
                    const L x(1, 2, 3);
                    EXPECT_EQ(
                            std::make_tuple(x.Pointer<0>(p), x.Pointer<1>(p), x.Pointer<2>(p)),
                            (Type<std::tuple<int8_t *, int8_t *, Int128 *>>(x.Pointers(p))));
                }
            }

            TEST(Layout, SliceByIndexSize) {
                alignas(max_align_t) const unsigned char p[100] = {};
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, L::Partial(0).Slice<0>(p).size());
                    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
                    EXPECT_EQ(3, L(3).Slice<0>(p).size());
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
                    EXPECT_EQ(5, L(3, 5).Slice<1>(p).size());
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
                    EXPECT_EQ(3, L::Partial(3, 5).Slice<0>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
                    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<0>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<1>(p).size());
                    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<2>(p).size());
                    EXPECT_EQ(3, L(3, 5, 7).Slice<0>(p).size());
                    EXPECT_EQ(5, L(3, 5, 7).Slice<1>(p).size());
                    EXPECT_EQ(7, L(3, 5, 7).Slice<2>(p).size());
                }
            }

            TEST(Layout, SliceByTypeSize) {
                alignas(max_align_t) const unsigned char p[100] = {};
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, L::Partial(0).Slice<int32_t>(p).size());
                    EXPECT_EQ(3, L::Partial(3).Slice<int32_t>(p).size());
                    EXPECT_EQ(3, L(3).Slice<int32_t>(p).size());
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(3, L::Partial(3).Slice<int8_t>(p).size());
                    EXPECT_EQ(3, L::Partial(3, 5).Slice<int8_t>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5).Slice<int32_t>(p).size());
                    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<int8_t>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<int32_t>(p).size());
                    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<Int128>(p).size());
                    EXPECT_EQ(3, L(3, 5, 7).Slice<int8_t>(p).size());
                    EXPECT_EQ(5, L(3, 5, 7).Slice<int32_t>(p).size());
                    EXPECT_EQ(7, L(3, 5, 7).Slice<Int128>(p).size());
                }
            }

            TEST(Layout, MutableSliceByIndexSize) {
                alignas(max_align_t) unsigned char p[100];
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, L::Partial(0).Slice<0>(p).size());
                    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
                    EXPECT_EQ(3, L(3).Slice<0>(p).size());
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
                    EXPECT_EQ(5, L(3, 5).Slice<1>(p).size());
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(3, L::Partial(3).Slice<0>(p).size());
                    EXPECT_EQ(3, L::Partial(3, 5).Slice<0>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5).Slice<1>(p).size());
                    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<0>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<1>(p).size());
                    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<2>(p).size());
                    EXPECT_EQ(3, L(3, 5, 7).Slice<0>(p).size());
                    EXPECT_EQ(5, L(3, 5, 7).Slice<1>(p).size());
                    EXPECT_EQ(7, L(3, 5, 7).Slice<2>(p).size());
                }
            }

            TEST(Layout, MutableSliceByTypeSize) {
                alignas(max_align_t) unsigned char p[100];
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0, L::Partial(0).Slice<int32_t>(p).size());
                    EXPECT_EQ(3, L::Partial(3).Slice<int32_t>(p).size());
                    EXPECT_EQ(3, L(3).Slice<int32_t>(p).size());
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(3, L::Partial(3).Slice<int8_t>(p).size());
                    EXPECT_EQ(3, L::Partial(3, 5).Slice<int8_t>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5).Slice<int32_t>(p).size());
                    EXPECT_EQ(3, L::Partial(3, 5, 7).Slice<int8_t>(p).size());
                    EXPECT_EQ(5, L::Partial(3, 5, 7).Slice<int32_t>(p).size());
                    EXPECT_EQ(7, L::Partial(3, 5, 7).Slice<Int128>(p).size());
                    EXPECT_EQ(3, L(3, 5, 7).Slice<int8_t>(p).size());
                    EXPECT_EQ(5, L(3, 5, 7).Slice<int32_t>(p).size());
                    EXPECT_EQ(7, L(3, 5, 7).Slice<Int128>(p).size());
                }
            }

            TEST(Layout, SliceByIndexData) {
                alignas(max_align_t) const unsigned char p[100] = {};
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<const int32_t>>(L::Partial(0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<const int32_t>>(L::Partial(3).Slice<0>(p)).data()));
                    EXPECT_EQ(0, Distance(p, Type<span<const int32_t>>(L(3).Slice<0>(p)).data()));
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<const int32_t>>(L::Partial(3).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p,
                                     Type<span<const int32_t>>(L::Partial(3, 5).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            12,
                            Distance(p,
                                     Type<span<const int32_t>>(L::Partial(3, 5).Slice<1>(p)).data()));
                    EXPECT_EQ(0,
                              Distance(p, Type<span<const int32_t>>(L(3, 5).Slice<0>(p)).data()));
                    EXPECT_EQ(12,
                              Distance(p, Type<span<const int32_t>>(L(3, 5).Slice<1>(p)).data()));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<const int8_t>>(L::Partial(0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<const int8_t>>(L::Partial(1).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<const int8_t>>(L::Partial(5).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<const int8_t>>(L::Partial(0, 0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p,
                                     Type<span<const int32_t>>(L::Partial(0, 0).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<const int8_t>>(L::Partial(1, 0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            4,
                            Distance(p,
                                     Type<span<const int32_t>>(L::Partial(1, 0).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<const int8_t>>(L::Partial(5, 3).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            8,
                            Distance(p,
                                     Type<span<const int32_t>>(L::Partial(5, 3).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p, Type<span<const int8_t>>(L::Partial(0, 0, 0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p,
                                    Type<span<const int32_t>>(L::Partial(0, 0, 0).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p,
                                    Type<span<const Int128>>(L::Partial(0, 0, 0).Slice<2>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p, Type<span<const int8_t>>(L::Partial(1, 0, 0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            4,
                            Distance(
                                    p,
                                    Type<span<const int32_t>>(L::Partial(1, 0, 0).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            8,
                            Distance(
                                    p,
                                    Type<span<const Int128>>(L::Partial(1, 0, 0).Slice<2>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p, Type<span<const int8_t>>(L::Partial(5, 3, 1).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            24,
                            Distance(
                                    p,
                                    Type<span<const Int128>>(L::Partial(5, 3, 1).Slice<2>(p)).data()));
                    EXPECT_EQ(
                            8,
                            Distance(
                                    p,
                                    Type<span<const int32_t>>(L::Partial(5, 3, 1).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(p, Type<span<const int8_t>>(L(5, 3, 1).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            24,
                            Distance(p, Type<span<const Int128>>(L(5, 3, 1).Slice<2>(p)).data()));
                    EXPECT_EQ(
                            8, Distance(p, Type<span<const int32_t>>(L(5, 3, 1).Slice<1>(p)).data()));
                }
            }

            TEST(Layout, SliceByTypeData) {
                alignas(max_align_t) const unsigned char p[100] = {};
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p, Type<span<const int32_t>>(L::Partial(0).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p, Type<span<const int32_t>>(L::Partial(3).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(p, Type<span<const int32_t>>(L(3).Slice<int32_t>(p)).data()));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<const int8_t>>(L::Partial(0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<const int8_t>>(L::Partial(1).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<const int8_t>>(L::Partial(5).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p, Type<span<const int8_t>>(L::Partial(0, 0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p,
                                    Type<span<const int32_t>>(L::Partial(0, 0).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p, Type<span<const int8_t>>(L::Partial(1, 0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            4,
                            Distance(
                                    p,
                                    Type<span<const int32_t>>(L::Partial(1, 0).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p, Type<span<const int8_t>>(L::Partial(5, 3).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            8,
                            Distance(
                                    p,
                                    Type<span<const int32_t>>(L::Partial(5, 3).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p,
                                    Type<span<const int8_t>>(L::Partial(0, 0, 0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<const int32_t>>(L::Partial(0, 0, 0).Slice<int32_t>(p))
                                    .data()));
                    EXPECT_EQ(0, Distance(p, Type<span<const Int128>>(
                            L::Partial(0, 0, 0).Slice<Int128>(p))
                            .data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p,
                                    Type<span<const int8_t>>(L::Partial(1, 0, 0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            4,
                            Distance(p, Type<span<const int32_t>>(L::Partial(1, 0, 0).Slice<int32_t>(p))
                                    .data()));
                    EXPECT_EQ(8, Distance(p, Type<span<const Int128>>(
                            L::Partial(1, 0, 0).Slice<Int128>(p))
                            .data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p,
                                    Type<span<const int8_t>>(L::Partial(5, 3, 1).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(24, Distance(p, Type<span<const Int128>>(
                            L::Partial(5, 3, 1).Slice<Int128>(p))
                            .data()));
                    EXPECT_EQ(
                            8,
                            Distance(p, Type<span<const int32_t>>(L::Partial(5, 3, 1).Slice<int32_t>(p))
                                    .data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<const int8_t>>(L(5, 3, 1).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            24,
                            Distance(p,
                                     Type<span<const Int128>>(L(5, 3, 1).Slice<Int128>(p)).data()));
                    EXPECT_EQ(
                            8, Distance(
                            p, Type<span<const int32_t>>(L(5, 3, 1).Slice<int32_t>(p)).data()));
                }
            }

            TEST(Layout, MutableSliceByIndexData) {
                alignas(max_align_t) unsigned char p[100];
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(0,
                              Distance(p, Type<span<int32_t>>(L::Partial(0).Slice<0>(p)).data()));
                    EXPECT_EQ(0,
                              Distance(p, Type<span<int32_t>>(L::Partial(3).Slice<0>(p)).data()));
                    EXPECT_EQ(0, Distance(p, Type<span<int32_t>>(L(3).Slice<0>(p)).data()));
                }
                {
                    using L = Layout<int32_t, int32_t>;
                    EXPECT_EQ(0,
                              Distance(p, Type<span<int32_t>>(L::Partial(3).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(p, Type<span<int32_t>>(L::Partial(3, 5).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            12,
                            Distance(p, Type<span<int32_t>>(L::Partial(3, 5).Slice<1>(p)).data()));
                    EXPECT_EQ(0, Distance(p, Type<span<int32_t>>(L(3, 5).Slice<0>(p)).data()));
                    EXPECT_EQ(12, Distance(p, Type<span<int32_t>>(L(3, 5).Slice<1>(p)).data()));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(0,
                              Distance(p, Type<span<int8_t>>(L::Partial(0).Slice<0>(p)).data()));
                    EXPECT_EQ(0,
                              Distance(p, Type<span<int8_t>>(L::Partial(1).Slice<0>(p)).data()));
                    EXPECT_EQ(0,
                              Distance(p, Type<span<int8_t>>(L::Partial(5).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(p, Type<span<int8_t>>(L::Partial(0, 0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(p, Type<span<int32_t>>(L::Partial(0, 0).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(p, Type<span<int8_t>>(L::Partial(1, 0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            4, Distance(p, Type<span<int32_t>>(L::Partial(1, 0).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(p, Type<span<int8_t>>(L::Partial(5, 3).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            8, Distance(p, Type<span<int32_t>>(L::Partial(5, 3).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<int8_t>>(L::Partial(0, 0, 0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<int32_t>>(L::Partial(0, 0, 0).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<Int128>>(L::Partial(0, 0, 0).Slice<2>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<int8_t>>(L::Partial(1, 0, 0).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            4,
                            Distance(p, Type<span<int32_t>>(L::Partial(1, 0, 0).Slice<1>(p)).data()));
                    EXPECT_EQ(
                            8, Distance(
                            p, Type<span<Int128>>(L::Partial(1, 0, 0).Slice<2>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<int8_t>>(L::Partial(5, 3, 1).Slice<0>(p)).data()));
                    EXPECT_EQ(
                            24, Distance(
                            p, Type<span<Int128>>(L::Partial(5, 3, 1).Slice<2>(p)).data()));
                    EXPECT_EQ(
                            8,
                            Distance(p, Type<span<int32_t>>(L::Partial(5, 3, 1).Slice<1>(p)).data()));
                    EXPECT_EQ(0, Distance(p, Type<span<int8_t>>(L(5, 3, 1).Slice<0>(p)).data()));
                    EXPECT_EQ(24,
                              Distance(p, Type<span<Int128>>(L(5, 3, 1).Slice<2>(p)).data()));
                    EXPECT_EQ(8, Distance(p, Type<span<int32_t>>(L(5, 3, 1).Slice<1>(p)).data()));
                }
            }

            TEST(Layout, MutableSliceByTypeData) {
                alignas(max_align_t) unsigned char p[100];
                {
                    using L = Layout<int32_t>;
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<int32_t>>(L::Partial(0).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<int32_t>>(L::Partial(3).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(0, Distance(p, Type<span<int32_t>>(L(3).Slice<int32_t>(p)).data()));
                }
                {
                    using L = Layout<int8_t, int32_t, Int128>;
                    EXPECT_EQ(
                            0, Distance(p, Type<span<int8_t>>(L::Partial(0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(p, Type<span<int8_t>>(L::Partial(1).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(p, Type<span<int8_t>>(L::Partial(5).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<int8_t>>(L::Partial(0, 0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<int32_t>>(L::Partial(0, 0).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<int8_t>>(L::Partial(1, 0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            4, Distance(
                            p, Type<span<int32_t>>(L::Partial(1, 0).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(p, Type<span<int8_t>>(L::Partial(5, 3).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            8, Distance(
                            p, Type<span<int32_t>>(L::Partial(5, 3).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<int8_t>>(L::Partial(0, 0, 0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p, Type<span<int32_t>>(L::Partial(0, 0, 0).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            0,
                            Distance(
                                    p,
                                    Type<span<Int128>>(L::Partial(0, 0, 0).Slice<Int128>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<int8_t>>(L::Partial(1, 0, 0).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            4,
                            Distance(
                                    p, Type<span<int32_t>>(L::Partial(1, 0, 0).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(
                            8,
                            Distance(
                                    p,
                                    Type<span<Int128>>(L::Partial(1, 0, 0).Slice<Int128>(p)).data()));
                    EXPECT_EQ(
                            0, Distance(
                            p, Type<span<int8_t>>(L::Partial(5, 3, 1).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            24,
                            Distance(
                                    p,
                                    Type<span<Int128>>(L::Partial(5, 3, 1).Slice<Int128>(p)).data()));
                    EXPECT_EQ(
                            8,
                            Distance(
                                    p, Type<span<int32_t>>(L::Partial(5, 3, 1).Slice<int32_t>(p)).data()));
                    EXPECT_EQ(0,
                              Distance(p, Type<span<int8_t>>(L(5, 3, 1).Slice<int8_t>(p)).data()));
                    EXPECT_EQ(
                            24,
                            Distance(p, Type<span<Int128>>(L(5, 3, 1).Slice<Int128>(p)).data()));
                    EXPECT_EQ(
                            8, Distance(p, Type<span<int32_t>>(L(5, 3, 1).Slice<int32_t>(p)).data()));
                }
            }

            MATCHER_P(IsSameSlice, slice, "") {
                return arg.size() == slice.size() && arg.data() == slice.data();
            }

            template<typename... M>
            class TupleMatcher {
            public:
                explicit TupleMatcher(M... matchers) : matchers_(std::move(matchers)...) {}

                template<typename Tuple>
                bool MatchAndExplain(const Tuple &p,
                                     testing::MatchResultListener * /* listener */) const {
                    static_assert(std::tuple_size<Tuple>::value == sizeof...(M), "");
                    return MatchAndExplainImpl(
                            p, abel::make_index_sequence<std::tuple_size<Tuple>::value>{});
                }

                // For the matcher concept. Left empty as we don't really need the diagnostics
                // right now.
                void DescribeTo(::std::ostream *os) const {}

                void DescribeNegationTo(::std::ostream *os) const {}

            private:
                template<typename Tuple, size_t... Is>
                bool MatchAndExplainImpl(const Tuple &p, abel::index_sequence<Is...>) const {
                    // Using std::min as a simple variadic "and".
                    return std::min(
                            {true, testing::SafeMatcherCast<
                                    const typename std::tuple_element<Is, Tuple>::type &>(
                                    std::get<Is>(matchers_))
                                    .Matches(std::get<Is>(p))...});
                }

                std::tuple<M...> matchers_;
            };

            template<typename... M>
            testing::PolymorphicMatcher<TupleMatcher<M...>> Tuple(M... matchers) {
                return testing::MakePolymorphicMatcher(
                        TupleMatcher<M...>(std::move(matchers)...));
            }

            TEST(Layout, Slices) {
                alignas(max_align_t) const unsigned char p[100] = {};
                using L = Layout<int8_t, int8_t, Int128>;
                {
                    const auto x = L::Partial();
                    EXPECT_THAT(Type<std::tuple<>>(x.Slices(p)), Tuple());
                }
                {
                    const auto x = L::Partial(1);
                    EXPECT_THAT(Type<std::tuple<span<const int8_t>>>(x.Slices(p)),
                                Tuple(IsSameSlice(x.Slice<0>(p))));
                }
                {
                    const auto x = L::Partial(1, 2);
                    EXPECT_THAT(
                            (Type<std::tuple<span<const int8_t>, span<const int8_t>>>(x.Slices(p))),
                            Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p))));
                }
                {
                    const auto x = L::Partial(1, 2, 3);
                    EXPECT_THAT((Type<std::tuple<span<const int8_t>, span<const int8_t>,
                            span<const Int128>>>(x.Slices(p))),
                                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
                                      IsSameSlice(x.Slice<2>(p))));
                }
                {
                    const L x(1, 2, 3);
                    EXPECT_THAT((Type<std::tuple<span<const int8_t>, span<const int8_t>,
                            span<const Int128>>>(x.Slices(p))),
                                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
                                      IsSameSlice(x.Slice<2>(p))));
                }
            }

            TEST(Layout, MutableSlices) {
                alignas(max_align_t) unsigned char p[100] = {};
                using L = Layout<int8_t, int8_t, Int128>;
                {
                    const auto x = L::Partial();
                    EXPECT_THAT(Type<std::tuple<>>(x.Slices(p)), Tuple());
                }
                {
                    const auto x = L::Partial(1);
                    EXPECT_THAT(Type<std::tuple<span<int8_t>>>(x.Slices(p)),
                                Tuple(IsSameSlice(x.Slice<0>(p))));
                }
                {
                    const auto x = L::Partial(1, 2);
                    EXPECT_THAT((Type<std::tuple<span<int8_t>, span<int8_t>>>(x.Slices(p))),
                                Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p))));
                }
                {
                    const auto x = L::Partial(1, 2, 3);
                    EXPECT_THAT(
                            (Type<std::tuple<span<int8_t>, span<int8_t>, span<Int128>>>(x.Slices(p))),
                            Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
                                  IsSameSlice(x.Slice<2>(p))));
                }
                {
                    const L x(1, 2, 3);
                    EXPECT_THAT(
                            (Type<std::tuple<span<int8_t>, span<int8_t>, span<Int128>>>(x.Slices(p))),
                            Tuple(IsSameSlice(x.Slice<0>(p)), IsSameSlice(x.Slice<1>(p)),
                                  IsSameSlice(x.Slice<2>(p))));
                }
            }

            TEST(Layout, UnalignedTypes) {
                constexpr Layout<unsigned char, unsigned char, unsigned char> x(1, 2, 3);
                alignas(max_align_t) unsigned char p[x.AllocSize() + 1];
                EXPECT_THAT(x.Pointers(p + 1), Tuple(p + 1, p + 2, p + 4));
            }

            TEST(Layout, CustomAlignment) {
                constexpr Layout<unsigned char, Aligned<unsigned char, 8>> x(1, 2);
                alignas(max_align_t) unsigned char p[x.AllocSize()];
                EXPECT_EQ(10, x.AllocSize());
                EXPECT_THAT(x.Pointers(p), Tuple(p + 0, p + 8));
            }

            TEST(Layout, OverAligned) {
                constexpr size_t M = alignof(max_align_t);
                constexpr Layout<unsigned char, Aligned<unsigned char, 2 * M>> x(1, 3);
                alignas(2 * M) unsigned char p[x.AllocSize()];
                EXPECT_EQ(2 * M + 3, x.AllocSize());
                EXPECT_THAT(x.Pointers(p), Tuple(p + 0, p + 2 * M));
            }

            TEST(Layout, Alignment) {
                static_assert(Layout<int8_t>::Alignment() == 1, "");
                static_assert(Layout<int32_t>::Alignment() == 4, "");
                static_assert(Layout<Int64>::Alignment() == 8, "");
                static_assert(Layout<Aligned<int8_t, 64>>::Alignment() == 64, "");
                static_assert(Layout<int8_t, int32_t, Int64>::Alignment() == 8, "");
                static_assert(Layout<int8_t, Int64, int32_t>::Alignment() == 8, "");
                static_assert(Layout<int32_t, int8_t, Int64>::Alignment() == 8, "");
                static_assert(Layout<int32_t, Int64, int8_t>::Alignment() == 8, "");
                static_assert(Layout<Int64, int8_t, int32_t>::Alignment() == 8, "");
                static_assert(Layout<Int64, int32_t, int8_t>::Alignment() == 8, "");
            }

            TEST(Layout, ConstexprPartial) {
                constexpr size_t M = alignof(max_align_t);
                constexpr Layout<unsigned char, Aligned<unsigned char, 2 * M>> x(1, 3);
                static_assert(x.Partial(1).template Offset<1>() == 2 * M, "");
            }

// [from, to)
            struct Region {
                size_t from;
                size_t to;
            };

            void ExpectRegionPoisoned(const unsigned char *p, size_t n, bool poisoned) {
#ifdef ADDRESS_SANITIZER
                for (size_t i = 0; i != n; ++i) {
                  EXPECT_EQ(poisoned, __asan_address_is_poisoned(p + i));
                }
#endif
            }

            template<size_t N>
            void ExpectPoisoned(const unsigned char (&buf)[N],
                                std::initializer_list<Region> reg) {
                size_t prev = 0;
                for (const Region &r : reg) {
                    ExpectRegionPoisoned(buf + prev, r.from - prev, false);
                    ExpectRegionPoisoned(buf + r.from, r.to - r.from, true);
                    prev = r.to;
                }
                ExpectRegionPoisoned(buf + prev, N - prev, false);
            }

            TEST(Layout, PoisonPadding) {
                using L = Layout<int8_t, Int64, int32_t, Int128>;

                constexpr size_t n = L::Partial(1, 2, 3, 4).AllocSize();
                {
                    constexpr auto x = L::Partial();
                    alignas(max_align_t) const unsigned char c[n] = {};
                    x.PoisonPadding(c);
                    EXPECT_EQ(x.Slices(c), x.Slices(c));
                    ExpectPoisoned(c, {});
                }
                {
                    constexpr auto x = L::Partial(1);
                    alignas(max_align_t) const unsigned char c[n] = {};
                    x.PoisonPadding(c);
                    EXPECT_EQ(x.Slices(c), x.Slices(c));
                    ExpectPoisoned(c, {{1, 8}});
                }
                {
                    constexpr auto x = L::Partial(1, 2);
                    alignas(max_align_t) const unsigned char c[n] = {};
                    x.PoisonPadding(c);
                    EXPECT_EQ(x.Slices(c), x.Slices(c));
                    ExpectPoisoned(c, {{1, 8}});
                }
                {
                    constexpr auto x = L::Partial(1, 2, 3);
                    alignas(max_align_t) const unsigned char c[n] = {};
                    x.PoisonPadding(c);
                    EXPECT_EQ(x.Slices(c), x.Slices(c));
                    ExpectPoisoned(c, {{1,  8},
                                       {36, 40}});
                }
                {
                    constexpr auto x = L::Partial(1, 2, 3, 4);
                    alignas(max_align_t) const unsigned char c[n] = {};
                    x.PoisonPadding(c);
                    EXPECT_EQ(x.Slices(c), x.Slices(c));
                    ExpectPoisoned(c, {{1,  8},
                                       {36, 40}});
                }
                {
                    constexpr L x(1, 2, 3, 4);
                    alignas(max_align_t) const unsigned char c[n] = {};
                    x.PoisonPadding(c);
                    EXPECT_EQ(x.Slices(c), x.Slices(c));
                    ExpectPoisoned(c, {{1,  8},
                                       {36, 40}});
                }
            }

            TEST(Layout, DebugString) {
                {
                    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial();
                    EXPECT_EQ("@0<signed char>(1)", x.DebugString());
                }
                {
                    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1);
                    EXPECT_EQ("@0<signed char>(1)[1]; @4<int>(4)", x.DebugString());
                }
                {
                    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1, 2);
                    EXPECT_EQ("@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)",
                              x.DebugString());
                }
                {
                    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1, 2, 3);
                    EXPECT_EQ(
                            "@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)[3]; "
                            "@16" +
                            Int128::Name() + "(16)",
                            x.DebugString());
                }
                {
                    constexpr auto x = Layout<int8_t, int32_t, int8_t, Int128>::Partial(1, 2, 3, 4);
                    EXPECT_EQ(
                            "@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)[3]; "
                            "@16" +
                            Int128::Name() + "(16)[4]",
                            x.DebugString());
                }
                {
                    constexpr Layout<int8_t, int32_t, int8_t, Int128> x(1, 2, 3, 4);
                    EXPECT_EQ(
                            "@0<signed char>(1)[1]; @4<int>(4)[2]; @12<signed char>(1)[3]; "
                            "@16" +
                            Int128::Name() + "(16)[4]",
                            x.DebugString());
                }
            }

            TEST(Layout, CharTypes) {
                constexpr Layout<int32_t> x(1);
                alignas(max_align_t) char c[x.AllocSize()] = {};
                alignas(max_align_t) unsigned char uc[x.AllocSize()] = {};
                alignas(max_align_t) signed char sc[x.AllocSize()] = {};
                alignas(max_align_t) const char cc[x.AllocSize()] = {};
                alignas(max_align_t) const unsigned char cuc[x.AllocSize()] = {};
                alignas(max_align_t) const signed char csc[x.AllocSize()] = {};

                Type<int32_t *>(x.Pointer<0>(c));
                Type<int32_t *>(x.Pointer<0>(uc));
                Type<int32_t *>(x.Pointer<0>(sc));
                Type<const int32_t *>(x.Pointer<0>(cc));
                Type<const int32_t *>(x.Pointer<0>(cuc));
                Type<const int32_t *>(x.Pointer<0>(csc));

                Type<int32_t *>(x.Pointer<int32_t>(c));
                Type<int32_t *>(x.Pointer<int32_t>(uc));
                Type<int32_t *>(x.Pointer<int32_t>(sc));
                Type<const int32_t *>(x.Pointer<int32_t>(cc));
                Type<const int32_t *>(x.Pointer<int32_t>(cuc));
                Type<const int32_t *>(x.Pointer<int32_t>(csc));

                Type<std::tuple<int32_t *>>(x.Pointers(c));
                Type<std::tuple<int32_t *>>(x.Pointers(uc));
                Type<std::tuple<int32_t *>>(x.Pointers(sc));
                Type<std::tuple<const int32_t *>>(x.Pointers(cc));
                Type<std::tuple<const int32_t *>>(x.Pointers(cuc));
                Type<std::tuple<const int32_t *>>(x.Pointers(csc));

                Type<span<int32_t>>(x.Slice<0>(c));
                Type<span<int32_t>>(x.Slice<0>(uc));
                Type<span<int32_t>>(x.Slice<0>(sc));
                Type<span<const int32_t>>(x.Slice<0>(cc));
                Type<span<const int32_t>>(x.Slice<0>(cuc));
                Type<span<const int32_t>>(x.Slice<0>(csc));

                Type<std::tuple<span<int32_t>>>(x.Slices(c));
                Type<std::tuple<span<int32_t>>>(x.Slices(uc));
                Type<std::tuple<span<int32_t>>>(x.Slices(sc));
                Type<std::tuple<span<const int32_t>>>(x.Slices(cc));
                Type<std::tuple<span<const int32_t>>>(x.Slices(cuc));
                Type<std::tuple<span<const int32_t>>>(x.Slices(csc));
            }

            TEST(Layout, ConstElementType) {
                constexpr Layout<const int32_t> x(1);
                alignas(int32_t) char c[x.AllocSize()] = {};
                const char *cc = c;
                const int32_t *p = reinterpret_cast<const int32_t *>(cc);

                EXPECT_EQ(alignof(int32_t), x.Alignment());

                EXPECT_EQ(0, x.Offset<0>());
                EXPECT_EQ(0, x.Offset<const int32_t>());

                EXPECT_THAT(x.Offsets(), ElementsAre(0));

                EXPECT_EQ(1, x.Size<0>());
                EXPECT_EQ(1, x.Size<const int32_t>());

                EXPECT_THAT(x.Sizes(), ElementsAre(1));

                EXPECT_EQ(sizeof(int32_t), x.AllocSize());

                EXPECT_EQ(p, Type<const int32_t *>(x.Pointer<0>(c)));
                EXPECT_EQ(p, Type<const int32_t *>(x.Pointer<0>(cc)));

                EXPECT_EQ(p, Type<const int32_t *>(x.Pointer<const int32_t>(c)));
                EXPECT_EQ(p, Type<const int32_t *>(x.Pointer<const int32_t>(cc)));

                EXPECT_THAT(Type<std::tuple<const int32_t *>>(x.Pointers(c)), Tuple(p));
                EXPECT_THAT(Type<std::tuple<const int32_t *>>(x.Pointers(cc)), Tuple(p));

                EXPECT_THAT(Type<span<const int32_t>>(x.Slice<0>(c)),
                            IsSameSlice(span<const int32_t>(p, 1)));
                EXPECT_THAT(Type<span<const int32_t>>(x.Slice<0>(cc)),
                            IsSameSlice(span<const int32_t>(p, 1)));

                EXPECT_THAT(Type<span<const int32_t>>(x.Slice<const int32_t>(c)),
                            IsSameSlice(span<const int32_t>(p, 1)));
                EXPECT_THAT(Type<span<const int32_t>>(x.Slice<const int32_t>(cc)),
                            IsSameSlice(span<const int32_t>(p, 1)));

                EXPECT_THAT(Type<std::tuple<span<const int32_t>>>(x.Slices(c)),
                            Tuple(IsSameSlice(span<const int32_t>(p, 1))));
                EXPECT_THAT(Type<std::tuple<span<const int32_t>>>(x.Slices(cc)),
                            Tuple(IsSameSlice(span<const int32_t>(p, 1))));
            }

            namespace example {

// Immutable move-only string with sizeof equal to sizeof(void*). The string
// size and the characters are kept in the same heap allocation.
                class CompactString {
                public:
                    CompactString(const char *s = "") {  // NOLINT
                        const size_t size = strlen(s);
                        // size_t[1], followed by char[size + 1].
                        // This statement doesn't allocate memory.
                        const L layout(1, size + 1);
                        // AllocSize() tells us how much memory we need to allocate for all our
                        // data.
                        p_.reset(new unsigned char[layout.AllocSize()]);
                        // If running under ASAN, mark the padding bytes, if any, to catch memory
                        // errors.
                        layout.PoisonPadding(p_.get());
                        // Store the size in the allocation.
                        // Pointer<size_t>() is a synonym for Pointer<0>().
                        *layout.Pointer<size_t>(p_.get()) = size;
                        // Store the characters in the allocation.
                        memcpy(layout.Pointer<char>(p_.get()), s, size + 1);
                    }

                    size_t size() const {
                        // Equivalent to reinterpret_cast<size_t&>(*p).
                        return *L::Partial().Pointer<size_t>(p_.get());
                    }

                    const char *c_str() const {
                        // Equivalent to reinterpret_cast<char*>(p.get() + sizeof(size_t)).
                        // The argument in Partial(1) specifies that we have size_t[1] in front of
                        // the characters.
                        return L::Partial(1).Pointer<char>(p_.get());
                    }

                private:
                    // Our heap allocation contains a size_t followed by an array of chars.
                    using L = Layout<size_t, char>;
                    std::unique_ptr<unsigned char[]> p_;
                };

                TEST(CompactString, Works) {
                    CompactString s = "hello";
                    EXPECT_EQ(5, s.size());
                    EXPECT_STREQ("hello", s.c_str());
                }

            }  // namespace example

        }  // namespace
    }  // namespace container_internal

}  // namespace abel
